Lens plasma coating system

ABSTRACT

The invention provides a method for plasma coating of optical lenses, particularly lenses made of silicone-containing polymer. The method of the invention comprising selectively depressurizing and pressurizing an entry hold chamber and an exit hold chamber while constantly maintaining a plasma gas in a coating chamber at a process pressure without depressurizing and pressurizing repeatedly the coating chamber, wherein the coating chamber is located between the entry hold chamber and the exit hold chamber.

This application is a division of U.S. patent application Ser. No.09/911,221 filed Jul. 23, 2001, now U.S. Pat. No. 6,881,269, whichclaims benefits under 35 U.S.C. §119(e) of U.S. provisional patentapplication No. 60/225,940 filed Aug. 17, 2000.

BACKGROUND OF THE INVENTION

The present invention relates to a system for coating contact lenses, orother optical lens devices, particularly those made ofsilicone-containing polymer. Hereinafter the term silicone polymers areused to indicate silicone-containing polymers suitable for ocular uses,including rigid silicone polymers, silicone elastomers and siliconehydrogels. The advantages of silicone polymers as contact lens materialshave long been recognized. However, silicone polymers have severaldisadvantages. For example, certain materials in the eye's tear filmtend to adhere to the lenses and reduce their optical clarity. Thesilicone lens, especially silicone elastomer or hydrogel lens, may betacky and this characteristic may render the lens to stick to thecornea, and the material's hydrophobic nature prevents the lens fromwetting.

To resolve these problems, it is known to apply a very thin hydrophiliccoating using electrical glow discharge polymerization. Generally, thecoating process involves placing a silicone lens core in, or moving itthrough, a plasma cloud so that the material adheres to the core.Although various materials may be used, hydrocarbons such as methane maybe used.

The polymerized coating provides a highly wettable surface withoutsignificantly, if at all, reducing the oxygen and carbon dioxidepermeability of the lens. It also provides an effective barrier againsttear film material that would otherwise adhere to the lens, therebypreventing the optical clarity degradation that would otherwise occur.

Conventional plasma polymerization lens coating techniques employ batchsystems in which one or more silicone lens cores are placed in a reactorchamber between opposing electrodes. The chamber is then sealed anddepressurized by a vacuum system. Significant time is required to pumpthe batch system to the operative pressure. When a suitable pressure isachieved in the chamber, a process gas is introduced into the chamberinterior, and the electrodes are energized. The resulting plasma cloudmay apply a thin polymer coating to the lens. After an appropriate time,the electrodes are de-energized, and the reactor chamber is brought backto atmospheric pressure so that the lenses may be removed.

It has been recognized that it is preferable to move the lenses throughthe plasma cloud. Thus, in certain systems, the silicone lens cores aremounted on a rotating wheel disposed between the electrodes so that thewheel carries the lenses through the cloud. These systems are sometimesdescribed as “continuous” systems to distinguish them from other batchsystems. However, all such systems are considered to be batch systemsfor purposes of the present disclosure in that each requires a reactorchamber that must be repeatedly pressurized and depressurized as one ormore groups of silicone lens cores are placed in and removed from thesystem.

One example of a batch system is provided in U.S. Pat. No. 4,312,575 toPeyman et al., the disclosure of which is incorporated by referenceherein for all purposes. In “Ultrathin Coating Of Plasma Polymer OfMethane Applied On The Surface Of Silicone Contact Lenses,” Journal ofBiomedical Materials Research, Vol. 22, 919–937 (1988), Peng Ho andYasuda describe a batch system including a bell-shaped vacuum chamber inwhich opposing aluminum electrodes are disposed. A rotatable aluminumplate sits between the electrodes and is driven by an induction motorwithin the system.

SUMMARY OF THE INVENTION

The present invention recognizes and addresses disadvantages of priorart constructions and methods.

Accordingly, it is an object of the present invention to provide animproved lens plasma coating system.

This and other objects are achieved by a system for treating the surfaceof an optical lens. The system includes an entry chamber having a firstentrance gate and a first exit gate. The first entrance gate and thefirst exit gate seal the entry chamber when the gates are closed. Theentry chamber includes a conveyor extending between the first entrancegate and the first exit gate. A first negative pressure source is inselective communication with the entry chamber. A coating chamber has asecond entrance gate and a second exit gate. The second entrance gateand the second exit gate seal the coating chamber when they are closed.The coating chamber includes a pair of spaced apart electrodes disposedtherein and a conveyor extending between the second entrance gate andthe second exit gate so that the conveyor conveys the lens between theelectrodes. A source of plasma gas is in communication with the coatingchamber to introduce the gas into the coating chamber. A second negativepressure source is in communication with the coating chamber. Anelectrical power source is in communication with the electrodes to applya predetermined electrical potential at each electrode so that, uponestablishment of a predetermined pressure in the coating chamber by thesecond negative pressure source, a plasma cloud of the gas isestablished between the electrodes. An exit chamber has a third entrancegate and a third exit gate. The third entrance gate and the third exitgate seal the exit chamber when they are closed, and the exit chamberincludes a conveyor extending between the third entrance gate and thethird exit gate. A third negative pressure source is in selectivecommunication with the exit chamber. The entry chamber communicates withthe coating chamber through the first exit gate and the second entrancegate so that the entry chamber conveyor and the coating chamber conveyorcommunicate to pass the lens from the entry chamber to the coatingchamber. The coating chamber communicates with the exit chamber throughthe second exit gate and the third entrance gate so that the coatingchamber conveyor and the exit chamber conveyor communicate to pass thelens from the coating chamber to the exit chamber.

A method for treating the surface of an optical lens according to thepresent invention includes providing first an optical lens and providinga coating chamber including a pair of spaced apart electrodes disposedtherein. A plasma gas is maintained in the coating chamber. A firstpredetermined pressure is maintained in the coating chamber, and apredetermined electric potential is maintained at each electrode so thata plasma cloud of gas is established between the electrodes. An entrychamber is provided upstream from the coating chamber, and the firstlens is moved into the entry chamber. Gas is introduced into at least aportion of the entry chamber adjacent the coating chamber, and at leastthat portion of the entry chamber is brought to the first predeterminedpressure. The entry chamber is brought into communication with thecoating chamber, and the first lens is moved from the entry chamber intothe coating chamber and through the plasma cloud. An exit chamber isprovided downstream from the coating chamber. Gas is introduced into atleast a portion of the exit chamber adjacent the coating chamber, and atleast that portion of the exit chamber is brought to the firstpredetermined pressure. The first lens is moved from the coating chamberto the exit chamber.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate one or more embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendeddrawings, in which:

FIG. 1A is a perspective view of a lens holding tray for use in a lenscoating system and method according to an embodiment of the presentinvention;

FIG. 1B is an enlarged perspective view of the holding tray as in FIG.1A;

FIG. 1C is a cross-sectional view taken along the line 1C—1C in FIG. 1B;

FIG. 2 is a perspective view of a lens tray carrier and a slug (i.e.carrier holding system) for use in a lens coating system and methodaccording to an embodiment of the present invention;

FIG. 3, presented on separate drawing sheets as FIGS. 3A and 3B, is aschematic illustration of a lens coating system according to anembodiment of the present invention;

FIG. 4A is a partial perspective view of a lens coating system accordingto an embodiment of the present invention;

FIG. 4B is a cross-sectional view taken along the line 4B—4B in FIG. 4A;

FIG. 4C is a partial perspective view of a lens coating system accordingto an embodiment of the present invention;

FIG. 5A is a partial perspective view of a lens coating system accordingto an embodiment of the present invention;

FIG. 5B is a cross-sectional view of a chamber and valve as shown inFIG. 5A;

FIG. 6A is a cross-sectional view of a lens coating system according toan embodiment of the present invention; and

FIG. 6B is a plan view of the interior magnetic arrangement of amagnetic device for use in a coating chamber of a lens coating systemaccording to an embodiment of the present invention.

Repeat use of reference characters in the present specification anddrawings is intended to represent same or analogous features or elementsof the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference will now be made in detail to presently preferred embodimentsof the invention, one or more examples of which are illustrated in theaccompanying drawings. Each example is provided by way of explanation ofthe invention, not limitation of the invention. In fact, it will beapparent to those skilled in the art that modifications and variationscan be made in the present invention without departing from the scope orspirit thereof. For instance, features illustrated or described as partof one embodiment may be used on another embodiment to yield a stillfurther embodiment. Thus, it is intended that the present inventioncovers such modifications and variations as come within the scope of theappended claims and their equivalents.

The present invention is directed to an optical lens coating system inwhich lens cores may enter, pass through and exit the system withoutrequiring the coating zone to be repeatedly pressurized anddepressurized. Although the discussion herein describes the use of amethane containing plasma cloud to apply a hydrophilic polymer coatingto silicone lens cores, it should be understood that this is forexemplary purposes only and that other plasma and lens materials may beused. For example, the system may employ any suitable plasma, whethergenerated of hydrocarbon or other appropriate material, that would applya desirable coating on a lens core. Additionally, the plasma may becomprised of an oxidizing gas so that the lens core surface is oxidizedto create a hydrophilic layer. As used herein, a “coating” includes sucha layer. Further, the system may be used in conjunction with lens coresmade of any material upon which it is desirable to place a coating.Thus, it should be understood by those skilled in this art that thedescription of silicone lens cores and methane plasma herein is notintended to limit the scope or spirit of the present invention.

Furthermore the system may use any suitable apparatus and method forgenerating plasma to treat lens cores. Such apparatus and methods shouldbe understood by those skilled in the art and are therefore notdiscussed in detail herein. Thus, it should also be understood that theparticular arrangement described below for generating plasma is providedfor exemplary purposes only.

Prior to entering the system, referring now to FIG. 1A, the lens coresare placed in a holding tray 10 having an outer frame 12 and verticalintermediate members 14. FIG. 1A illustrates an exemplary holding tray.Seven rows of wire holders 16 extend between each adjacent verticalmember. In the two outer columns 18 and 20, each row contains fourholders, while each row in the two inner columns 22 and 24 includesthree holders. Thus, the tray includes ninety-eight holders in all.

Referring to FIGS. 1B and 1C, each holder 16 includes an annular wirerim 26 and five wire stems 28 extending radially inward therefrom. Alens core 30 is placed in each holder so that it sits on the stems 28.Holder 16 is described in more detail in commonly-assigned U.S. Pat. No.5,874,127, the entire disclosure of which is incorporated by referenceherein.

Referring again to FIG. 1A, and also referring to FIG. 2, each holdingtray 10 includes a pair of hooks 32 on the opposing outer verticalmembers 14 of frame 12. Corresponding hooks 34 on a tray carrier 36receive hooks 32 so that holding tray 10 may be hung on the traycarrier. In the embodiment shown in FIG. 2, carrier 36 may hold fourholding trays 10 and, therefore, up to three hundred ninety two lenscores.

Referring now to FIGS. 3A and 3B, the tray carrier is placed into alinear plasma coating system 40. Initially, the trays move through adrying chamber comprised of five subchambers (hereinafter referred to as“zones”) 42A–42E, each approximately five meters long. The tray carrierremains for a total of about twenty minutes in the drying chamber for adesired time, say about twenty minutes or sufficient to meet thenecessary vacuum and coating application target.

Because the lens cores may contain a hydrophilic material, they can behygroscopic and therefore can absorb water from the environment. Thus,it may be desirable to allow drying time. The dry zones maintain aconstant relative humidity level, e.g., at or below ten percent topermit further drying, if necessary, and also provide a dry buffer areain which to place lens cores prior to entering the coating zones.

Referring also to FIGS. 2, 4A and 4B, each tray carrier is received in arectangular slot 44 defined as a “slug” 46. A pair of bolts secures thecarrier in the slug. A bore 48 extends through slug 46 beneath the traycarrier. The drying chamber includes a conveyor to transport the slugand carrier (hereinafter referred to collectively as the “carrier”unless otherwise indicated). The conveyor is comprised of individualconveyors in the zones 42A–42E, each extending between opposing wheels52 and 54. A servo motor 56 drives the conveyor and may be controlled bya personal computer, main frame system or other programmable logiccircuit (hereinafter referred to generally as “PLC”). Two side members58 sit on respective sides of the conveyor, and rollers 60 are disposedin gaps 62 in each side member to guide the tray carrier as it passesbetween the side members.

A light source 64 mounted in one side member directs light across to theother side member, where it is detected by a light detector 66. Thelight source and light detector are aligned so that light passes betweenthem through bore 48 in slug 46. Light detector 66 outputs a signal tothe PLC which, in turn, controls servo motor 56. Accordingly, the PLCdetects the carrier's presence as the slug initially breaks the lightbeam between source 64 and detector 66 upon entering the first dry zone42A. Other carrier detection systems may be utilized in lieu of thelight detector; for example pressure or contact microswitches may alsobe employed. When bore 48 reaches the light source/detector pair,detector 66 again detects the light beam, and the PLC stops servo motor56 for an approximate preprogrammed time say four minutes. At the end ofthis time, the PLC again activates motor 56 so that the carrier ispassed to the second dry zone, 42B. Dry zone 42B has a conveyor, motorand side member pair like that of zone 42A, except that an additionalmechanism is included in zone 42B to rotate the side members andconveyor ninety degrees so that the carrier may be passed to zone 42C.In each zone, however, a light source/detector pair is provided todetect the presence of a carrier in the zone. The PLC moves the carrierfrom one dry zone to the next if no carrier is still waiting in thesubsequent zone.

The entrance to zone 42A may be open or may have a suitable covering asappropriate for a given system. A respective duct 68 feeds from asuitable air handling system (not shown) and directs the conditioned airor gas to each dry zone. Suitable ventilation ducts may also beprovided. The air conditioning system may be independently controlled tocontinuously provide properly temperature-controlled and humidified airto the ducts, e.g., at approximately 70° F. +/−2°.

Referring again to FIGS. 3A and 3B, the PLC moves the carrier through aslit valve 72 into an entry lock 70 if the carrier has been in dry zone42E for a sufficient duration, if no carrier is waiting in entry lock70, and if suitable conditions exist in entry lock 70 as described inmore detail below. Entry lock 70 includes a conveyor 50 and side members58 as in the dry zones. A light source/detector pair is also provided sothat the PLC senses when the carrier is fully within the entry lock. ThePLC then stops the servo motor that drives the conveyor and closes theslit valves at the entry lock's entrance and exit to seal the entrylock.

Referring also to FIGS. 5A and 5B, the entrance slit valve 72 includes adoor 74 having a sealing material 76 that lines the periphery of itsinside surface. Door 74 is hinged so that it is movable by a linkage 78between an open and closed position. The PLC controls linkage 78. Whenthe door is in its closed position, seal 76 surrounds and seals anentrance passage 80 into entry lock 70.

When the light source/detector in entry lock 70 detects the presence ofthe carrier through bore 48 (FIG. 2), the PLC closes the slit valves atboth ends of entry lock 70. The entry lock is a stainless steel chamberwith which inlets, outlets and sensors may communicate as discussedbelow. It is a closed chamber except for the slit valves. Thus, when thevalves are closed, the entry lock is sealed.

When the carrier is in the entry lock, and the chamber is sealed, thePLC activates a valve 82 and a pump 84 to pump out the entry lock andthereby create a vacuum condition therein. Specifically, the pump bringsthe interior area of entry lock 70 from ambient pressure to a desiredpreset lower pressure, e.g., at or below one mTorr. The PLC monitors theentry lock's pressure by a pressure sensor 85 extending through theentry lock's housing.

It should be understood that while the entry lock housing, as well asthe housings of the entry hold, entry buffer, coating, exit buffer, exithold and exit lock chambers discussed below, may all made of stainlesssteel, the housings may be made of any suitable material and in anysuitable construction. Further, the housings for the five dry zones andof the five exits zones discussed below may be made from a rigid polymersuch as polymethylmethacrylate (PMMA), but may also be made from steelor other suitable material.

When the PLC is notified from pressure sensor 85 that the interiorpressure of entry lock 70 is at or below the preset lower pressure, andthat a preset minimum time has lapsed, say 290 seconds, since valve 82was activated, the PLC opens slit valve 86 between entry lock 70 and anentry hold chamber and activates the conveyors in both the entry lockand the entry hold so that the carrier is moved into the entry hold.

The entry hold also includes vertical side members and a lightsource/detector pair. When the slug bore 48 (FIG. 2) aligns with thelight detector and thereby indicates to the PLC that the carrier isfully in the entry hold, the PLC closes slit valve 86 and a slit valve90 to seal the entry hold. After closing valve 90, the PLC activates avalve 92 that opens a gas line 94 connected to a source (not shown) ofdry gas, e.g., nitrogen, to the interior of entry lock 70. The PLCcontinues to vent the entry lock with the dry gas until pressure sensor84 indicates atmospheric pressure in the entry lock. The PLC then opensslit valve 72 so that the entry lock can receive the next carrier.

The gas is “dry” in that it has a low water content, for example lessthan three ppm. A dry vent gas is preferred to prevent undesired waterabsorption by the lens cores or the chamber walls. In a preferredembodiment, a single source of dry gas is used to provide the vent gasto line 94 as well as to the vent lines for other chambers downstreamfrom the entry lock. Thus, it should be understood that while thechambers are referred to herein as having “respective” vent sources,this includes a construction where all the vent lines may be fed by thesame ultimate source of vent gas. Similarly, while individual vacuumpumps are shown in FIG. 3 and described herein, it should be understoodthat pumping lines to multiple chambers may communicate with the samesource of negative pressure.

Before opening valve 86, the PLC brings entry hold 88 to a pressure lessthan or equal to the set low pressure by activating a valve 98 thatopens the entry hold interior to a vacuum pump 100. When pressuresensors 85 and 102 indicate that the entry lock pressure and the entryhold pressure are equal, +/−5 mT, the PCL opens slit valve 86 to movethe carrier into the entry hold.

Despite the prior drying stages, the lens cores may still contain somewater. The entry hold therefore acts both as a buffer and a dryingstage. Repeated pumping to create vacuum conditions in the entry holddraws water vapor from the chamber's walls, and potentially from lenscores, thereby creating a dry environment. Dry gas is used to vent thechamber through a valve 104 operated by the PLC to maintain thiscondition. When the carrier enters the entry hold, and the PLC seals thechamber, valve 98 remains open so that pump 100 draws water vapor fromthe tray carrier, slug and lens cores.

When the PLC determines that when sufficient time has elapsed sinceclosing slit valves 86 and 90, it closes valve 98 and opens a valve 106between a mass flow controller 108 and the entry hold interior. The massflow controller, the construction and operation of which should beunderstood by those skilled in the art, may be controlled independentlyof the PLC in this embodiment and introduces process gas from a commonline 110 into the entry hold.

When pressure sensor 102 indicates that the internal pressure of entryhold 88 is approximately the desired level, the PLC opens slit valve 90and activates the conveyor motors in the entry hold and in an entrybuffer 112 to move the carrier into the entry buffer. Again, the entrybuffer includes vertical side members 58 and a light source/detectorpair that enables the PLC to determine when the slug bore aligns withthe light source and detector, thereby indicating that the carrier isfully within the entry buffer. The PLC then closes slit valve 90 andcontinues to pump the entry hold through valve 98 until the entry holdreaches the desired preset lower pressure. At that time, provided theother conditions discussed above are also met, the PLC opens the slitvalve 86 and moves the next carrier into the entry hold.

The entry buffer helps isolate the downstream coating zone fromnon-process gasses that might otherwise flow to the coating zones fromthe entry hold. It also acts as a waiting chamber for a carrier waitingto enter the coating zones. It is maintained at the process pressurethrough a valve 114 that is controlled by the PLC and that opens theentry buffer to a vacuum pump 116. The PLC monitors pressure in theentry buffer by a pressure sensor 118 and introduces the process gas tothe entry buffer through a valve 120 connected to process gas line 110through a mass flow controller 122. When necessary, the PLC can vent theentry buffer with dry gas through a valve 124.

From the entry buffer, the carrier moves through tandem coating zones126 and 128. The PLC maintains the coating zones at approximately theprocess pressure by pressure valves 130 and 132 that expose the coatingzone interiors to the vacuum pumps 133 and 134. The PLC provides processgas to the coating zones by valves 136 and 138 that are connected toprocess gas line 110 through mass flow controllers 140 and 142. While asingle valve/mass flow controller is shown in this embodiment for eachcoating zone, it should be understood that a respective such pair may beprovided for the front half and the back half of each chamber toindependently control the flow of gas to each half. If necessary, thePLC can vent the coating zones with dry gas through valves 144 and 146.The PLC monitors pressure in the coating zones through pressure sensors148/149 and 150/151.

An exit buffer 152 follows the second coating zone 128. As with theentry buffer and the coating zones, it includes a conveyor and servomotor that may be operated by the PLC. It also includes vertical members58 and a light source and detector pair. The PLC maintains the processpressure level in the exit buffer through a valve 154 opening to avacuum pump 156. The PLC monitors pressure in the exit buffer through apressure sensor 158 and controls the flow of process gas from line 110into the exit buffer from a mass flow controller 160 by a valve 162.

There are no slit valves between entry buffer 112 and first coating zone126, between first coating zone 126 and second coating zone 128, orbetween second coating zone 128 and exit buffer 152. Instead, severalsteel shoulders 164 extend partially laterally into the system to createa channel extending from the entry buffer through the two coating zonesto the exit buffer. Thus, the entry buffer chamber, coating zones andexit buffer chamber define a segmented common chamber. As noted above,the PLC maintains this common chamber at the process pressure, andmaintains process gas in the chamber, during the system's operationthrough respective valves and mass flow controllers. Because of theselective pressurization and depressurization of the entry holddiscussed above, and of the exit hold discussed below, the system maycoat lens cores on successive tray carriers without having to pressurizeand depressurize the coating zones.

The illustrated coating zones 126 and 128 are identically constructed.For ease of explanation, therefore, only the structure of coating zone126 is described herein.

Coating zone 126 includes two tandemly arranged magnetrons, each havinga pair of opposing electrodes 166 and 168. The use of a magnetron isoptional, depending on the application. Referring to the schematiccross-sectional view in FIG. 6A, the coating zone does not includevertical members 58 (FIGS. 4A–4B) that would otherwise interfere withthe application of the plasma cloud to the lens cores. The cloud iscreated by electrodes 166 and 168, which include rectangular titaniumplates 170 and 172. Each titanium plate is separated from a respectivemagnetic device 174 and 176 by four 2 mm–3 mm ceramic buttons 178. Eachtitanium plate is approximately 50 centimeters high, 1/16 inches thickand 18 centimeters long.

Each magnetic device 174 and 176 may include an outer metal box, forexample made of stainless steel, through which cooling water may bepumped from tubes 180. Referring also to FIG. 6B, the interior of eachbox includes a rectangular central steel core 182 and a surroundingrectangular steel ring 184. A series of permanent magnets 186 extendbetween core 182 and ring 184 and are arranged in a north-south patternas shown in FIG. 6B so that central core 182 is a magnetic “south” poleand outer ring 184 is a magnetic “north” pole. Although the exactopposite can also be employed, i.e., the north/south magnets may betotally reversed. Each permanent magnet is separated from adjacentparallel magnets by an approximately two inch gap. Titanium plates 170and 172 are driven to the same electric potential by an AC power source188 through a transformer 190. The strength of the magnets may be variedto control the extent of the plasma by one skilled in the art.

A distance of approximately seven to ten centimeters separates titaniumplates 172 and 178. When energized, the plates create a plasma cloudbetween them as should be understood in the art. The 2 mm–3 mm gapbetween the titanium plates and their respective magnetic devices is sosmall, however, that no sufficient plasma occurs there. The magneticfield created by the magnetic devices behind the titanium plates alsoprevents plasma formation. This creates a predictable, stable andrelatively uniform plasma cloud between the plates. While an intenselyglowing rectangular plasma area 188 is created immediately in front ofeach of the titanium plates, a plasma cloud 190 between areas 188 hasless plasma definition but more uniformity. Specifically, it is moreuniform in the vertical direction. Cloud 190 sits above conveyor 50, andit is therefore through this cloud that the lens cores are moved.

Referring again to FIGS. 3A and 3B, each electrode pair 166/168 includesits own pressure sensor 148/149 and vacuum throttle valve 130. As notedabove, each electrode pair may also include its own process gas throttlevalve. The PLC constantly monitors the pressure in the area in whicheach electrode pair is disposed and adjusts valves 130 and 136accordingly to maintain the processing pressure condition. That is, inone embodiment, the process gas flow rate into the area is constant.Throttle valves 130, however, are set to the processing pressure and,therefore, control the out flow rate to maintain the desired pressure.Thus, the uniform plasma clouds remain consistent from one electrodepair to the next. Further, the process gas inlet from each valve 136 isplaced behind one of the electrodes 166 or 168 so that the flow from theprocess gas line is blocked by the electrodes and does not disturb theplasma cloud. Other gas diversion schemes may be designed thataccomplish the same end, but using the electrode pair is a convenientsolution.

In one embodiment of the present invention, the process gas is seventypercent methane and thirty percent air (a dry mixture of nitrogen andoxygen). It was been found that including oxygen in the process gasprovides highly useful means for maintaining the reaction (plasma)chamber clear of deposits such that the coating zone does not have to becleaned routinely. As can be appreciated, in a continuous plasmaapparatus, it is highly advantageous to utilize a processing gas thatprevents or diminishes deposits from accumulating in the coatingchamber, especially on the electrodes.

As noted above, coating zones 126 and 128 do not include verticalmembers or light source/detector pairs. Instead, the PLC runs the servomotors in each zone at a constant speed so that the respective conveyorsrun continuously at preset desired speed, say five m/sec. Thus, once acarrier is driven onto the conveyor in zone 126 from the conveyor in theentry buffer, it moves continuously through the four magnetrons in thetwo coating zones.

The PLC begins a timer when the light detector in the entry bufferindicates that a carrier moves from the entry buffer conveyor to theconveyor in the coating zone 126 and sends a subsequent carrier from theentry buffer into the coating zone only upon expiration of this timer.In one preferred embodiment, the length of the timer is three hundredseconds, which provides enough time for the exit buffer to move adownstream carrier to an exit hold chamber 196, thereby preventingcarriers from stacking up in the coating zones.

Exit hold 196 is the mirror of the entry hold. The PLC creates a vacuumby a pump 198 through a valve 200. It monitors pressure in the exit holdby a pressure sensor 202 and controls the introduction of process gasfrom line 110 and a mass flow controller 204 by a valve 206.

When pressure sensor 202 indicates that the exit hold pressure isapproximately the coating zone pressure say fifty mTorr, and the lightdetector in exit buffer 152 indicates that a carrier is present in theexit buffer, the PLC opens a slit valve 208 between the exit buffer andthe exit hold and activates the conveyors in the exit hold and exitbuffer to transfer the carrier to the exit hold. When the light detectorin the exit hold-determines that the transfer is complete, the PLCcloses slit valve 208 and a slit valve 210 at the exit hold's downstreamend, thereby sealing the exit hold. The PLC then throttles valve 200 toremove the process gas and bring the exit hold to less than or equal toone mTorr, or some other desired vacuum pressure.

An exit lock chamber 197 is downstream from the exit hold. Prior toopening slit valve 210, the PLC pumps the exit lock to a pressure ofless than or equal to the set low pressure by throttling a valve 210controlling the application of a vacuum pump 212 to the exit lockinterior. When the PLC determines from pressure sensor 202 and apressure sensor 214 in the exit lock that the exit hold pressure and theexit lock pressure are approximately equal and at or less than the setlow pressure, it opens slit valve 210 and activates the exit hold andexit lock conveyors to move the carrier to the exit lock. At this point,the PLC closes slit valve 210 and a slit valve 216 and vents the exitlock with dry gas by throttling a valve 218 until pressure sensor 214indicates that the exit lock pressure has reached an ambient level. Ifthe PLC detects an ambient pressure condition in the exit lock and thata carrier is present in the exit lock, it opens slit valve 216 andactivates the conveyors in the exit lock and a first exit zone 220A tomove the carrier to the exit zone. When a light detector in the exitzone indicates that the carrier has been transferred, the PLC closesslit valve 216 and pumps exit lock 197 back to the set low pressure toreceive the next carrier.

The construction of the exit zones 220A–220E is similar to that of dryzones 42A–42E. They may be removed from the final zone 220 manually orby an automatic system so that the now-coated lenses exit in the holders16 (FIG. 1).

It should be understood that the above discussion presents one or morepreferred embodiments of the present invention and that various suitableembodiments may fall within the scope and spirit of the presentinvention. The embodiments depicted are presented by way of example onlyand are not intended as limitations upon the present invention, and itshould be understood by those of ordinary skill in the art that thepresent invention is not limited to such embodiments since modificationscan be made. Therefore, it is contemplated that any and all suchembodiments are included in the present invention as may fall within theliteral or equivalent scope of the appended claims.

1. A method for treating the surface of optical lenses, said methodcomprising the steps of: (A) providing a plasma coating systemcomprising a coating chamber including a pair of spaced apart electrodesdisposed therein, an entry chamber upstream from the coating chamber,and an exit chamber downstream from the coating chamber, wherein theentry chamber includes an entry hold chamber adjacent to the coatingchamber, wherein the exit chamber includes an exit hold chamber adjacentto the coating chamber, wherein each of the coating chamber, the entryhold chamber, and the exit hold chamber, independent of each other, isin communication both with a negative pressure source and with a sourceof a plasma gas; (B) preparing the coating chamber for coating theoptical lenses, wherein the step of preparing the coating chambercomprises (i) filling the coating chamber with the plasma gas, (ii)constantly maintaining the plasma gas in the coating chamber at aprocess pressure by using the negative pressure and plasma gas sourcesof the coating chamber, and (iii) maintaining a predetermined electricpotential at each said electrode so that a plasma cloud of said plasmagas is established between said electrodes; (C) moving a lens into saidentry hold chamber; (D) sealing and vacuuming the entry hold chamberwith the lens for a period of time; (E) bringing said entry hold chamberto said process pressure by filing it with said plasma gas; (F) bringingsaid entry hold chamber into communication with said coating chamber;(G) moving said first lens from said entry hold chamber into saidcoating chamber and through said plasma cloud; (H) introducing saidplasma gas into said exit hold chamber until reaching said processpressure; (I) bring the exit hold chamber in communication with thecoating chamber; (J) moving said first lens from said coating chamber tosaid exit hold chamber, (K) repeating the steps from step (C) to step(J) for each lens to be treated, wherein the method is characterized inthat the coating chamber is not depressurized and pressurizedrepeatedly.
 2. The method as in claim 1, wherein said plasma gas is apolymerizable gas.
 3. The method of claim 2, wherein the plasma gascontains oxygen.
 4. The method as in claim 1, wherein the entry chambercomprises an entry lock chamber upstream from the entry hold chamber,wherein the entry lock chamber is in communication with but sealable offfrom the entry hold chamber, wherein step (C) includes moving said firstlens into said entry lock chamber before moving it into the entry holdchamber, wherein said method includes, following step (C) but beforestep (D), the steps (L) bringing said entry lock chamber and said entryhold chamber to a predetermined pressure, (M) bringing said entry lockchamber into communication with said entry hold chamber and moving saidlens from said entry lock chamber into said entry hold chamber, and (N)sealing said entry hold chamber from said entry lock chamber.
 5. Themethod as in claim 4, wherein said process pressure and saidpredetermined pressure are unequal.
 6. The method of claim 4, whereinthe plasma gas contains oxygen.
 7. The method as in claim 1, wherein thecoating chamber includes a plurality of pairs of spaced apartelectrodes, wherein the pairs are tandemly arranged in said coatingchamber.
 8. The method as in claim 1, wherein said exit chamber has anexit lock chamber, said exit lock chamber being downstream from and incommunication with said exit hold chamber, said method includes,following step (J), the steps (L) evacuating said plasma gas from saidexit hold chamber, (M) bringing said exit lock chamber to a pressureequal to the pressure in said exit hold chamber, (N) bringing said exithold chamber into communication with said exit lock chamber and movingsaid lens from said exit hold chamber into said exit lock chamber, and(O) sealing said exit lock chamber from said exit hold chamber.
 9. Themethod of claim 8, wherein the plasma gas contains oxygen.
 10. A methodfor applying a polymer coating to optical lenses, said method comprisingthe steps of: (A) providing said optical lenses on a plurality ofcarriers; (B) providing a plasma coating system comprising a coatingchamber including a plurality of pairs of spaced apart electrodesdisposed in tandem therein, an entry chamber upstream from the coatingchamber, and an exit chamber downstream from the coating chamber,wherein the entry chamber includes an entry hold chamber adjacent to thecoating chamber and entry lock chamber upstream from the entry lockchamber, wherein the exit chamber includes an exit hold chamber adjacentto the coating chamber, wherein each of the coating chamber, the entryhold chamber, and the exit hold chamber, independent of each other, isin communication both with a negative pressure source and with a sourceof a plasma gas, wherein the plasma gas is a polymerizable gas; (C)preparing the coating chamber for coating the optical lenses, whereinthe step of preparing the coating chamber comprises (i) filling thecoating chamber with the plasma gas, (ii) constantly maintaining theplasma gas in the coating chamber at a process pressure by using thenegative pressure and plasma gas sources of the coating chamber, and(iii) maintaining a predetermined electric potential at each saidelectrode so that a plasma cloud of said plasma gas is establishedbetween said electrodes; (D) moving a carrier with optical lenses intosaid entry lock chamber; (E) sealing said entry lock chamber andthereafter bringing said entry lock chamber to a predetermined lowpressure; (F) bringing said entry hold chamber to said predetermined lowpressure; (G) opening said entry hold chamber to said entry lock chamberand moving said carrier from said entry lock chamber into said entryhold chamber; (H) following step (G), sealing said entry hold chamberfrom said entry lock chamber, introducing said plasma gas into saidentry hold chamber until it reaching process pressure; (I) followingstep (G), bringing said entry lock chamber to ambient pressure, bringinganother carrier into said entry lock, and repeating said methodbeginning at step (E) with respect to said another carrier and for adesired number of subsequent carriers; (J) following step (H), openingsaid coating chamber to said entry hold chamber and moving said carrierinto said coating chamber and through said plasma clouds; (K) after saidcarrier is removed from said entry hold chamber in step (J), sealingsaid entry hold chamber from said coating chamber and said entry lockchamber and returning to step (F) with respect to said another carrier;(L) following step (J), introducing said plasma gas into said exit holdchamber until reaching said process pressure; (M) bringing said exithold chamber to said process pressure; and (Q) moving said carrier fromsaid coating chamber to said exit hold chamber, wherein the method ischaracterized in that the coating chamber is not depressurized andpressurized repeatedly.
 11. The method of claim 10, wherein the plasmagas contains oxygen.
 12. A continuous method for treating the surface ofoptical lenses, said method comprising the steps of: (A) providing saidoptical lenses in batches, (B) providing a plasma coating systemcomprising a coating chamber including a pair of spaced apart electrodesdisposed therein, an entry chamber upstream from the coating chamber,and an exit chamber downstream from the coating chamber, wherein theentry chamber includes an entry hold chamber adjacent to the coatingchamber, wherein the exit chamber includes an exit hold chamber adjacentto the coating chamber, wherein each of the coating chamber, the entryhold chamber, and the exit hold chamber, independent of each other, isin communication both with a negative pressure source and with a sourceof a plasma gas, wherein the entry hold chamber and the exit holdchamber, independently of each other are sealable from other chambers,and (C) selectively depressurizing and pressurizing the entry holdchamber and the exit hold chamber with the plasma gas before bring themin communication with the coating chamber while continuously maintainingthe plasma gas in a coating chamber at a process pressure between saidbatches without depressurizing and pressurizing repeatedly the coatingchamber, maintaining a plasma gas in said coating chamber, wherein saidplasma gas is produced from a process gas containing oxygen.